IgG Endopeptidase in Highly Sensitized Patients Undergoing Transplantation

Jordan et al, N Eng J Med 2017;377: 442-53


Donor-specific antibodies create an immunologic barrier to transplantation. Current therapies to modify donor-specific antibodies are limited and ineffective in the most highly HLA-sensitized patients. The IgG-degrading enzyme derived from Streptococcus pyogenes(IdeS), an endopeptidase, cleaves human IgG into F(ab′)2 and Fc fragments inhibiting complement-dependent cytotoxicity and antibody-dependent cellular cytotoxicity, which suggests that IdeS might be useful for desensitization. We report on the combined experience of two independently performed open-label, phase 1–2 trials (conducted in Sweden and the United States) that assessed the efficacy of IdeS with regard to desensitization and transplantation of a kidney from an HLA-incompatible donor.

We administered IdeS to 25 highly HLA-sensitized patients (11 patients in Uppsala or Stockholm, Sweden, and 14 in Los Angeles) before the transplantation of a kidney from an HLA-incompatible donor. Frequent monitoring for adverse events, outcomes, donor-specific antibodies, and renal function was performed, as were renal biopsies. Immunosuppression after transplantation consisted of tacrolimus, mycophenolate mofetil, and glucocorticoids. Patients in the U.S. study also received intravenous immune globulin and rituximab after transplantation to prevent antibody rebound.

Recipients in the U.S. study had a significantly longer cold ischemia time (the time elapsed between procurement of the organ and transplantation), a significantly higher rate of delayed graft function, and significantly higher levels of class I donor-specific antibodies than those in the Swedish study. A total of 38 serious adverse events occurred in 15 patients (5 events were adjudicated as being possibly related to IdeS). At transplantation, total IgG and HLA antibodies were eliminated. A total of 24 of 25 patients had perfusion of allografts after transplantation. Antibody-mediated rejection occurred in 10 patients (7 patients in the U.S. study and 3 in the Swedish study) at 2 weeks to 5 months after transplantation; all these patients had a response to treatment. One graft loss, mediated by non-HLA IgM and IgA antibodies, occurred.

IdeS reduced or eliminated donor-specific antibodies and permitted HLA-incompatible transplantation in 24 of 25 patients. (Funded by Hansa Medical; numbers, NCT02224820, NCT02426684, and NCT02475551.)

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Enzymatic inactivation of endogenous IgG by IdeS enhances therapeutic antibody efficacy.

Järnum et al., Mol Cancer Ther. 2017 May 22. pii: molcanther.0108.2017.

Endogenous plasma IgG sets an immunological threshold that dictates the activity of tumor-directed therapeutic antibodies. Saturation of cellular antibody receptors by endogenous antibody limits antibody-dependent cell-mediated cytotoxicity (ADCC) and antibody dependent cellular phagocytosis (ADCP). Here we show how enzymatic cleavage of IgG using the bacterial enzyme IdeS can be utilized to empty both high and low affinity Fcγ-receptors and clear the entire endogenous antibody pool. Using in vitro models, tumor animal models as well as ex vivo analysis of sera collected during a previous clinical trial with IdeS, we show how clearing of competing plasma antibody levels with IdeS unblocks cellular antibody receptors. We show that therapeutic antibodies against breast cancer (trastuzumab), colon cancer (cetuximab) and lymphomas (rituximab and alemtuzumab) can be potentiated when endogenous IgG is removed. Overall, IdeS is shown to be a potent tool to reboot the human antibody repertoire and to generate a window to preferentially load therapeutic antibodies onto effector cells and thereby create an armada of dedicated tumor seeking immune cells.

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IgG-degrading enzyme of Streptococcus pyogenes (IdeS) prevents disease progression and facilitates improvement in a rabbit model of Guillain-Barré syndrome.

Wang et al., Exp Neurol. 2017 May;291:134-140

Autoantibodies binding to peripheral nerves followed by complement deposition and membrane attack complex formation results in nerve damage in Guillain-Barré syndrome (GBS). Strategies to remove the pathogenic autoantibodies or block the complement deposition benefit most patients with GBS. Immunoglobulin G-degrading enzyme of Streptococcus pyogenes (IdeS) is a cysteine protease which cleaves IgG antibodies into F(ab')2 and Fc fragments. In this study, using a rabbit model of axonal GBS, acute motor axonal neuropathy (AMAN), we demonstrated that IdeS treatment significantly reduced the disruption of Nav channels as well as activated C3 deposition at the anterior spinal root nodes of Ranvier in AMAN rabbits. IdeS significantly promoted the clinical recovery of AMAN rabbits and there were significant lower frequencies of axonal degeneration in anterior spinal roots of AMAN rabbits with IdeS treatment compared to the saline controls. Our data support that IdeS treatment is a promising therapeutic strategy for GBS.

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The Bacterial Enzyme IdeS Cleaves the IgG-Type of B Cell Receptor (BCR), Abolishes BCR-Mediated Cell Signaling and Inhibits Memory B Cell Activation

Jarnum et al, J Immunol. 2015 Nov 9. pii: 1501929


Ag binding to the BCR is a critical step in B cell development and activation, initiating a cascade of signaling events ultimately leading to proliferation, differentiation, or cell death. A bacterial enzyme, IgG-degrading enzyme of Streptococcus pyogenes (IdeS), was shown to specifically cleave IgG molecules below the hinge region of soluble IgG and when IgG is bound to Ag, resulting in one F(ab')2 molecule and one homodimeric Fc fragment. Whether IdeS could also cleave the IgG molecule when it is present in the BCR attached to the B cell membrane in a complex with CD79a and CD79b is unknown. In this article, we present human in vitro and ex vivo data showing that IdeS cleaves the IgG present in the BCR complex and very efficiently blocks Ag binding to the BCR. As a consequence of IdeS cleaving the BCR, signaling cascades downstream of the BCR are blocked, and memory B cells are temporarily silenced, preventing them from responding to antigenic stimulation and their transition into Ab-producing cells.

Streptococcal IdeS: therapeutic potential for Guillain-Barré syndrome.

Takahashi et al., Sci Rep. 2015 Jul 21;5:10809

Plasma exchange and intravenous immunoglobulin are effective in treating Guillain–Barré syndrome (GBS) probably because the former removes IgG autoantibodies and complement and the latter inhibits complement activation subsequent to the autoantibody binding to peripheral nerve antigens. IgG degrading enzyme of Streptococcus pyogenes (IdeS) can cleave the pathogenic autoantibodies into F(ab’)2 and Fc. The purpose of this study is to show whether IdeS has novel therapeutic potential for GBS. Sera with anti-ganglioside IgG antibodies from 15 patients with GBS or Miller Fisher syndrome were used. We tested whether IdeS cleaved the anti-ganglioside IgG antibodies and inhibited deposition of activated complement component on ELISA plates. IdeS efficiently cleaved IgG and blocked complement activation mediated by anti-GM1, anti-GD1a and anti-GQ1b IgG antibodies. IdeS has therapeutic potential for GBS and related conditions.

Complete Removal of Extracellular IgG Antibodies in a Randomized Dose-Escalation Phase I Study with the Bacterial Enzyme IdeS – A Novel Therapeutic Opportunity

Winstedt et al. PLOS ONE, July 15, 2015

IdeS is a streptococcal protease that cleaves IgG antibodies into F(ab’)2 and Fc fragments with a unique degree of specificity, thereby providing a novel treatment opportunity of IgG-driven autoimmune conditions and antibody mediated transplant rejection. Here we report the results from a first in man, double blinded and randomized study with single ascending doses of IdeS in healthy, male subjects. Twenty healthy subjects were given intravenous single ascending doses of IdeS. With impressive efficacy IdeS cleaved the entire plasma IgG-pool only minutes after dosing. IgG reached nadir 6-24 hours after dosing and then slowly recovered. The half-life of IdeS was 4.9 (±2.8) hours at 0.24 mg/kg with the main fraction eliminated during 24 hours. Already two hours after IdeS-dosing, the phagocytic capacity of IgG/IgG-fragments was reduced to background levels. Importantly, IdeS has the capacity to inactivate Fc-mediated effector function in vivo, was considered safe with no serious adverse events, and without dose limiting toxicity in this study. The complete, rapid, but temporary removal of IgG provides a new potent therapeutic opportunity in IgG-mediated pathogenic conditions.

Successful treatment of experimental glomerulonephritis with IdeS and EndoS, IgG-degrading streptococcal enzymes

Yang et al. NEPHROLOGY DIALYSIS TRANSPLANTATION, Vol. 25, Issue 8, 2479-2486, March 2010

BACKGROUND: Anti-glomerular basement membrane (anti-GBM) disease often results in end-stage renal failure despite therapy with plasma exchange and immunosuppressive drugs. The newly discovered streptococcal enzymes IgG-degrading enzyme of S.pyogenes (IdeS) and endoglycosidase S (EndoS) act with remarkable specificity on circulating IgG. In this study, we investigate their ability in vivo to prevent damage mediated by kidney-bound antibodies in a mouse model of anti-GBM disease.

METHODS: Anti-GBM disease was induced in mice by injection of subnephritogenic doses of rabbit anti-mouse GBM, followed a week later by injection of monoclonal mouse anti-rabbit IgG antibodies. By administrating IdeS or EndoS as fusion partners with GST between these antibody injections, we tested their ability to prevent damage by acting on kidney-bound rabbit anti-GBM. Control animals received placebo injections.

RESULTS: All animals in the positive control groups developed severe albuminuria immediately after the second antibody injection (mean, 2.51 mg/24 h; range, 0.13-8.20). This was significantly diminished by EndoS (1.3 +/- 1.3 mg/24 h) and completely prevented by IdeS (0.017 +/- 0.014 mg/24 h). Immunofluorescence studies showed that IdeS treatment effectively removed the Fc fragments of the rabbit IgG. This was accompanied by a significant reduction of the deposition of the complement components C3 and C1q, and this diminished the recruitment of leukocytes to the glomeruli.

CONCLUSION: IdeS degrades IgG bound to the GBM in vivo, thereby preventing renal damage in this animal model. Most likely, IdeS would degrade both circulating and kidney-bound anti-GBM in patients with Goodpasture's disease. Whether this would lead to a halt in disease progression and a better prognosis remains to be determined.

Therapeutic cleavage of IgG: new avenues for treating inflammation

Nandakumar et al. TRENDS IN IMMUNOLOGY, Vol. 29, Issue 4, Apr 2008

Autoantibodies developing in humans contribute to the pathogenesis of several diseases, and injected therapeutic antibodies can also trigger adverse side effects. An efficient and rapid elimination of these antibodies are therefore critically needed. Antibody removal by plasmapheresis and immunoadsorption are commonly used methods but have their own limitations. Bacterial enzymes that can cleave IgG molecules or remove carbohydrate moieties to ameliorate their immunogenicity or effector functions in vivo offer new avenues for drug development. Recent discoveries highlight the possibility of cleaving or modifying IgG in vivo by injection of enzymes. Such an approach opens up new therapeutic possibilities not only for the control of pathogenic antibody-mediated inflammatory diseases but also allograft rejection or the treatment of side-effects of 'biologicals' such as monoclonal antibodies.

Cleaving antibodies in vivo with a bacterial enzyme - a novel therapeutic concept

Johansson et al. PLOS ONE, Feb 2008, Vol 3, Issue 2

BACKGROUND: IdeS, a proteinase from Streptococcus pyogenes, cleaves immunoglobulin (Ig)G antibodies with a unique degree of specificity. Pathogenic IgG antibodies constitute an important clinical problem contributing to the pathogenesis of a number of autoimmune conditions and acute transplant rejection. To be able to effectively remove such antibodies is therefore an important clinical challenge.

METHODOLOGY/PRINCIPAL FINDINGS: IdeS was found to specifically and efficiently cleave IgG in human blood in vitro (20 µg of IdeS caused a complete degradation of IgG in one ml of human whole blood in 15 minutes) and to clear IgG from the blood stream of rabbits in vivo (no IgG was detected six hours following an intravenous injection of 5 mg of IdeS) without any side effects. In a mouse model of immune thrombocytopenic purpura (ITP), polyclonal IgG antibodies against platelet surface antigens were used to induce a lethal disease. These profoundly thrombocytopenic animals were treated and cured by a single injection of IdeS.

CONCLUSIONS/SIGNIFICANCE: Novel information is provided concerning the IgG-cleaving activity of IdeS in vitro and in vivo. The highly specific and rapid elimination of IgG in vivo, the dramatic effect in a mouse model of ITP, and the lack of side effects in the treated animals, indicate that IdeS could also be used to treat IgG-driven diseases in humans.

Blocking of experimental arthritis by cleavage of IgG antibodies in vivo

Nandakumar et al. ARTHRITIS & RHEUMATISM, Vol. 56, Issue 10 , pp. 3253-3260, Oct. 2007

OBJECTIVE: To investigate whether IgG-degrading enzyme of Streptococcus pyogenes (IdeS), a bacterial cysteine endopeptidase that cleaves human IgG in the hinge region, can be used for blocking the development of arthritis.

METHODS: Recombinant IdeS was purified and tested for specificity against mouse IgG. IdeS was injected intravenously into mice with collagen antibody-induced arthritis (CAIA), collagen-induced arthritis (CIA), or relapsing CIA, and its effects on arthritis development and severity were assessed.

RESULTS: IdeS efficiently cleaved mouse IgG2a/c and IgG3 in vitro. Even at low dosage (10 microg), IdeS specifically cleaved IgG2a in vivo without any apparent side effects. IdeS treatment efficiently blocked CAIA induced by IgG2a antibodies. No effect was observed when arthritis was induced with IgG2b anti-type II collagen antibodies; since IdeS does not cleave IgG2b, this indicated that IgG cleavage was the mechanism of action. IdeS treatment reduced the severity of arthritis if administered within 24 hours after the onset of clinical arthritis, but did not block ongoing severe arthritis. IdeS treatment also significantly prevented an antibody-induced relapse in mice that had chronic arthritis, and delayed the onset and reduced the severity of arthritis in classic CIA.

CONCLUSION: IdeS has therapeutic potential in IgG antibody-mediated autoimmune arthritis, representing a new and unique means of blocking pathogenic antibodies.

Enzymatic characterization of the streptococcal endopeptidase, IdeS, reveals that it is a cysteine protease with strict specificity for IgG cleavage due to exosite binding

Vincents et al. BIOCHEMISTRY 2004, 43, 15540-15549

Streptococcus pyogenes, an important pathogen in humans, secretes an IgG specific endopeptidase named IdeS. To elucidate the mechanism that is responsible for this specificity, we have here characterized the activity of IdeS in detail. Both gamma chains of human IgG or its Fc fragment were cleaved in the hinge region after Gly236 by IdeS, but other proteins or synthetic peptides containing sequences such as the P(4)-P(1) segment in the IgG cleavage site, or long peptides resembling the IgG hinge, were not hydrolyzed at all. This is likely due to a second binding site interacting with the Fc part of IgG. The lack of IdeS activity on peptide substrates necessitated the development of an assay with IgG as the substrate for kinetic studies. IdeS showed a sigmoidal velocity curve at physiological IgG concentrations, and a declining enzyme rate at higher IgG concentrations. This atypical velocity curve suggests product inhibition and/or allosteric control, which again indicates the presence of an exosite involved in substrate binding. The pseudoequilibrium constant for IdeS hydrolysis of IgG was 90 microM. The enzyme exhibited activity in the pH range of 5.1-7.6, with an optimum at pH 6.6. IdeS was stable above pH 10 but not at acidic pH. It exhibited an activity maximum around 37 degrees C and a decreased thermal stability at 42 degrees C. Iodoacetate and iodoacetamide inhibited IdeS, as expected for a cysteine protease, and biochemical evidence verified this classification. E-64 and chicken cystatin, specific inhibitors of family C1 and C13 cysteine proteases, were without effect on enzyme activity, as were class specific serine, aspartic, and metallo protease inhibitors. No significant similarities were found in protein sequence comparisons with known enzyme families, suggesting that IdeS represents a novel family of cysteine proteases.

Structure of the streptococcal endopeptidase IdeS, a cysteine proteinase with strict specificity for IgG

Wenig et al. PNAS Dec. 2004, Vol. 101, No. 50, pp. 17371-17376

Pathogenic bacteria have developed complex and diverse virulence mechanisms that weaken or disable the host immune defense system. IdeS (IgG-degrading enzyme of Streptococcus pyogenes) is a secreted cysteine endopeptidase from the human pathogen S. pyogenes with an extraordinarily high degree of substrate specificity, catalyzing a single proteolytic cleavage at the lower hinge of human IgG. This proteolytic degradation promotes inhibition of opsonophagocytosis and interferes with the killing of group A Streptococcus. We have determined the crystal structure of the catalytically inactive mutant IdeS-C94S by x-ray crystallography at 1.9-A resolution. Despite negligible sequence homology to known proteinases, the core of the structure resembles the canonical papain fold although with major insertions and a distinct substrate-binding site. Therefore IdeS belongs to a unique family within the CA clan of cysteine proteinases. Based on analogy with inhibitor complexes of papain-like proteinases, we propose a model for substrate binding by IdeS.

IdeS, a novel streptococcal cysteine protease with unique specificity for immunoglobulin G

Von Pawel Rammingen et al. THE EMBO JOURNAL Vol. 21, No. 7 pp. 1607-1615, 2002

Recent work from several laboratories has demonstrated that proteolytic mechanisms significantly contribute to the molecular interplay between Streptococcus pyogenes, an important human pathogen, and its host. Here we describe the identification, purification and characterization of a novel extracellular cysteine proteinase produced by S.pyogenes. This enzyme, designated IdeS for Immunoglobulin G-degrading enzyme of S.pyogenes, is distinct from the well-characterized streptococcal cysteine proteinase, SpeB, and cleaves human IgG in the hinge region with a high degree of specificity. Thus, other human proteins, including immunoglobulins M, A, D and E, are not degraded by IdeS. The enzyme efficiently cleaves IgG antibodies bound to streptococcal surface structures, thereby inhibiting the killing of S.pyogenes by phagocytic cells. This and additional observations on the distribution and expression of the ideS gene indicate that IdeS represents a novel and significant bacterial virulence determinant, and a potential therapeutic target.


IgG glycan hydrolysis by EndoS inhibits experimental autoimmune encephalomyelitis

Benkhoucha et al., J Neuroinflammation. 2012 Sep 3;9:209

Studies in experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis, have shown that B cells markedly influence the course of the disease, although whether their effects are protective or pathological is a matter of debate. EndoS hydrolysis of the IgG glycan has profound effects on IgG effector functions, such as complement activation and Fc receptor binding, suggesting that the enzyme could be used as an immunomodulatory therapeutic agent against IgG-mediated diseases. We demonstrate here that EndoS has a protective effect in myelin oligodendrocyte glycoprotein peptide amino acid 35-55 (MOG(35-55))-induced EAE, a chronic neuroinflammatory demyelinating disorder of the central nervous system (CNS) in which humoral immune responses are thought to play only a minor role. EndoS treatment in chronic MOG(35-55)-EAE did not impair encephalitogenic T cell priming and recruitment into the CNS of mice, consistent with a primary role of EndoS in controlling IgG effector functions. In contrast, reduced EAE severity coincided with poor serum complement activation and deposition within the spinal cord, suggesting that EndoS treatment impairs B cell effector function. These results identify EndoS as a potential therapeutic agent against antibody-mediated CNS autoimmune disorders.

Enzymatic autoantibody glycan hydrolysis alleviates autoimmunity against type VII collagen

Hirose et al., J Autoimmun. 2012 Dec;39(4):304-14. doi: 10.1016/j.jaut.2012.04.002. Epub 2012 May 30

Autoantibody-mediated diseases comprise a heterogeneous group of disorders in which the pathogenic potential of autoantibodies has been clearly demonstrated. In general, their treatment relies on the long-term use of systemic corticosteroids and other immunosuppressants that are associated with considerable adverse reactions. EndoS, an endoglycosidase derived from Streptococcus pyogenes, specifically hydrolyzes the N-linked glycan of native IgG and has previously been shown to modulate the interaction between the Fc portion of autoantibody and Fcγ receptors on leukocytes. Here, different models of autoimmunity to type VII collagen, a structural protein of the dermal-epidermal junction (DEJ), were employed to explore the therapeutic potential of EndoS. First, pretreatment of otherwise pathogenic anti-murine type VII collagen (mCOL7) IgG with EndoS significantly reduced split formation at the DEJ in cryosections of murine skin and abrogated clinical disease in mice. Next, the effect of EndoS was also seen when the enzyme was injected into mice after pathogenic anti-mCOL7 IgG had been administered. Finally, to mimic the patient situation even closer, EndoS was applied in mice that had already developed clinical disease after immunization with mCOL7. In all EndoS-treated mice, disease progression was stopped, and in the majority of mice, clinical disease even regressed. Of note, EndoS was shown to hydrolyze already in vivo-bound pathogenic autoantibodies. In addition, EndoS treatment decreased lesional expression of activating FcγRs while increasing FcγRIIB expression.

IgG glycan hydrolysis by endoglycosidase S diminishes the proinflammatory properties of immune complexes from patients with systemic lupus erythematosus: a possible new treatment?

Lood et al., Arthritis Rheum. 2012 Aug;64(8):2698-706. doi: 10.1002/art.34454

Objective: Systemic lupus erythematosus (SLE) is an autoimmune disease with chronic or episodic inflammation in several organ systems, related to the presence of circulating and tissue-deposited immune complexes (ICs) that stimulate leukocytes through Fcγ receptors (FcγR) with subsequent inflammation. Treatment with endoglycosidase S (EndoS), an IgG glycan-hydrolyzing bacterial enzyme from Streptococcus pyogenes, has shown beneficial effects in several experimental animal models of chronic inflammatory disease. This study was undertaken to investigate whether EndoS affects the proinflammatory properties of ICs and has the potential to be developed as a therapy for SLE.

Methods: ICs purified from SLE patients or RNA-containing ICs formed in vitro were treated with EndoS and used in several assays reflecting different important features of SLE pathogenesis, such as phagocytosis by polymorphonuclear cells (PMNs) and plasmacytoid dendritic cells (PDCs), complement activation, and interferon-α (IFNα) production by PDCs.

Results: EndoS treatment abolished all proinflammatory properties of the ICs investigated. This included FcγR-mediated phagocytosis by PDCs (P = 0.001) and subsequent production of IFNα (P = 0.002), IC-induced classical pathway of complement activation (P = 0.008), chemotaxis, and oxidative burst activity of PMNs (P = 0.002). EndoS treatment also had a direct effect on the molecular structure of ICs, causing decreased IC size and glycosylation.

Conclusion: Our findings indicate that EndoS treatment has prominent effects on several pathogenetically important IC-mediated events, and suggest that EndoS has the potential to be developed as a novel therapy for SLE.

IgG glycan hydrolysis attenuates ANCA-mediated glomerulonephritis

van Timmeren et al., J Am Soc Nephrol. 2010 Jul;21(7):1103-14.

Anti-neutrophil cytoplasmic autoantibodies (ANCA) directed against myeloperoxidase (MPO) and proteinase 3 (Pr3) are considered pathogenic in ANCA-associated necrotizing and crescentic glomerulonephritis (NCGN) and vasculitis. Modulation of ANCA IgG glycosylation may potentially reduce its pathogenicity by abolishing Fc receptor-mediated activation of leukocytes and complement. Here, we investigated whether IgG hydrolysis by the bacterial enzyme endoglycosidase S (EndoS) attenuates ANCA-mediated NCGN. In vitro, treatment of ANCA IgG with EndoS significantly attenuated ANCA-mediated neutrophil activation without affecting antigen-binding capacity. In a mouse model of anti-MPO IgG/LPS-induced NCGN, we induced disease with either unmodified or EndoS-treated (deglycosylated) anti-MPO IgG. In separate experiments, we administered EndoS systemically after disease induction with unmodified anti-MPO IgG. Pretreatment of anti-MPO IgG with EndoS reduced hematuria, leukocyturia, and albuminuria and attenuated both neutrophil influx and formation of glomerular crescents. After inducing disease with unmodified anti-MPO IgG, systemic treatment with EndoS reduced albuminuria and glomerular crescent formation when initiated after 3 but not 24 hours. In conclusion, IgG glycan hydrolysis by EndoS attenuates ANCA-induced neutrophil activation in vitro and prevents induction of anti-MPO IgG/LPS-mediated NCGN in vivo. Systemic treatment with EndoS early after disease induction attenuates the development of disease. Thus, modulation of IgG glycosylation is a promising strategy to interfere with ANCA-mediated inflammatory processes.

The IgG-specific endoglycosidase EndoS inhibits both cellular and complement-mediated autoimmune hemolysis

Alphorn et al., Blood. 2010 Jun 17;115(24):5080-8.

EndoS from Streptococcus pyogenes is an immunomodulating enzyme that specifically hydrolyzes glycans from human immunoglobulin G and thereby affects antibody effector functions. Autoimmune hemolytic anemia is caused by antibody-mediated red blood cell (RBC) destruction and often resists treatment with corticosteroids that also cause frequent adverse effects. We show here that anti-RhD (anti-D) and rabbit anti-human-RBC antibodies (anti-RBC) mediated destruction of RBC, ie, phagocytosis, complement activation, and hemolysis in vitro and in vivo was inhibited by EndoS. Phagocytosis by monocytes in vitro was inhibited by pretreatment of anti-D with EndoS before sensitization of RBCs and abrogated by direct addition of EndoS to blood containing sensitized RBCs. The toxic effects of monocytes stimulated with anti-D-sensitized RBCs, as measured by interleukin-8 secretion and oxygen metabolite production, was restrained by EndoS. Agglutination of RBCs and complement-mediated hemolysis in vitro in whole human blood caused by rabbit anti-RBCs was inhibited by EndoS. Development of anemia in mice caused by a murine anti-RBC immunoglobulin G2a monoclonal autoantibody and complement activation and erythrophagocytosis by Kupffer cells in the liver were reduced by EndoS. Our data indicate that EndoS is a potential therapeutic agent that might be evaluated as an alternative to current treatment regimens against antibody-mediated destruction of RBCs.

Sugar-free antibodies–the bacterial solution to autoimmunity?

Allhorn et al., Ann N Y Acad Sci. 2009 Sep;1173:664-9.

The enzyme EndoS from Streptococcus pyogenes is an immunomodulatory molecule hydrolyzing the conserved glycans in the effector part of immunoglobulin G (IgG). EndoS is remarkably specific for IgG, and hydrolysis has profound effects on IgG effector functions. EndoS pretreatment of IgG, or direct administration to animals with experimental antibody-mediated autoimmune diseases, inhibits development of disease or cures animals from established disease. The properties of EndoS make it a unique experimental tool and an attractive alternative to current therapies of conditions involving pathogenic antibodies. This review describes the discovery of EndoS, the effects of EndoS on IgG effector functions in vitro and in vivo, the biotechnological potential of EndoS, and the outcomes of EndoS treatment in animal models of autoimmunity.

IgG glycan hydrolysis by a bacterial enzyme as a therapy against autoimmune conditions

Collin et al., Proc Natl Acad Sci U S A. 2008 Mar 18;105(11):4265-70.

EndoS from Streptococcus pyogenes efficiently hydrolyzes the functionally important and conserved N-linked glycan of IgG in human blood. Repeated i.v. administration of EndoS in rabbits completely hydrolyzes the glycans of the whole IgG pool, despite the generation of anti-EndoS antibodies. EndoS administration had no apparent effects on the health of the animals. EndoS hydrolysis of the IgG glycan has profound effects on IgG effector functions, such as complement activation and Fc receptor binding, suggesting that the enzyme could be used as an immunomodulatory therapeutic agent against IgG-mediated diseases. We demonstrate here that EndoS indeed has a protective effect in a mouse model of lethal IgG-driven immune (or idiopathic) thrombocytopenic purpura. EndoS pretreatment of pathogenic antibodies inhibits the development of disease, and the enzyme also rescues mice from already established disease when severe thrombocytopenia and s.c. bleeding have developed. These results identify EndoS as a potential therapeutic agent against diseases where pathogenic IgG antibodies are important and further emphasize antibody glycans as possible targets in future therapies against antibody-mediated autoimmune conditions.

Human IgG/Fc gamma R interactions are modulated by streptococcal IgG glycan hydrolysis

Allhorn et al., PLOS ONE. 2008 Jan 9;3(1):e1413.

The human pathogen Streptococcus pyogenes produces an endoglycosidase, EndoS that hydrolyzes the chitobiose core of the asparagine-linked glycan on the heavy chain of human IgG. IgG-binding to Fc gamma receptors (Fc gamma R) on leukocytes triggers effector functions including phagocytosis, oxidative burst and the release of inflammatory mediators. The interactions between Fc gamma R and the Fc domain of IgG depend on the IgG glycosylation state.

METHODOLOGY/PRINCIPAL FINDINGS: Here we show for the first time that EndoS hydrolyzes the heavy chain glycan of all four human IgG subclasses (IgG1-4), in purified form and in a plasma environment. An inactive form of EndoS, obtained by site-directed mutagenesis, binds IgG with high affinity, in contrast to wild type EndoS that only transiently interacts with IgG, as shown by Slot-blotting and surface plasmon resonance technology. Furthermore, EndoS hydrolysis of the IgG glycan influences the binding of IgG to immobilized soluble Fc gamma R and to an erythroleukemic cell line, K562, expressing Fc gamma RIIa. Incubation of whole blood with EndoS results in a dramatic decrease of IgG binding to activated monocytes as analyzed by flow cytometry. Moreover, the IgG bound to K562 cells dissociates when cells are treated with EndoS. Likewise, IgG bound to immobilized Fc gamma RIIa and subsequently treated with EndoS, dissociates from the receptor as analyzed by surface plasmon resonance and Western blot.

CONCLUSIONS/SIGNIFICANCE: We provide novel information about bacterial enzymatic modulation of the IgG/Fc gamma R interaction that emphasizes the importance of glycosylation for antibody effector functions. Moreover, EndoS could be used as a biochemical tool for specific IgG N-glycan hydrolysis and IgG purification/detection, or as a potential immunosuppressing agent for treatment of antibody-mediated pathological processes.

Endoglycosidase treatment abrogates IgG arthritogenicity: importance of IgG glycosylation in arthritis

Nandakumar et al., Eur J Immunol. 2007 Oct;37(10):2973-82

The glycosylation status of IgG has been implicated in the pathology of rheumatoid arthritis. Earlier, we reported the identification of a novel secreted endo-beta-N-acetylglucosaminidase (EndoS), secreted by Streptococcus pyogenes that specifically hydrolyzes the beta-1,4-di-N-acetylchitobiose core of the asparagine-linked glycan of human IgG. Here, we analyzed the arthritogenicity of EndoS-treated collagen type II (CII)-specific mouse mAb in vivo. Endoglycosidase treatment of the antibodies inhibited the induction of arthritis in (BALB/c x B10.Q) F1 mice and induced a milder arthritis in B10.RIII mice as compared with the severe arthritis induced by non-treated antibodies. Furthermore, EndoS treatment did not affect the binding of IgG to CII and their ability to activate complement, but it resulted in reduced IgG binding to FcgammaR and disturbed the formation of stable immune complexes. Hence, the asparagine-linked glycan on IgG plays a crucial role in the development of arthritis.

EndoS and SpeB from Streptococcus pyogenes inhibit immunoglobulin-mediated opsonophagocytosis

Collin et al., Infect Immun. 2002 Dec;70(12):6646-51

The human pathogen Streptococcus pyogenes primarily infects the upper respiratory tract and skin, but occasionally it disseminates and causes severe invasive disease with high mortality. This study revealed that the activity of extracellular EndoS, which hydrolyzes the functionally important N-linked oligosaccharides on opsonizing immunoglobulin G (IgG), contributes to increased survival of S. pyogenes in human blood ex vivo. The inability to kill the bacteria is due to reduced binding of IgG to Fc receptors and impaired classical pathway-mediated activation of complement. In addition, the activity of extracellular SpeB, which cleaves IgG into Fc and Fab fragments, also increases bacterial survival. This suggests that S. pyogenes expresses two enzymes, EndoS and SpeB, which modulate IgG by different mechanisms in order to evade the adaptive immune system.


Heparin-Binding Protein Measurement Improves the Prediction of Severe Infection With Organ Dysfunction in the Emergency Department

Crit Care Med. 2015 Nov;43(11):2378-86.

Objectives: Early identification of patients with infection and at risk of developing severe disease with organ dysfunction remains a difficult challenge. We aimed to evaluate and validate the heparin-binding protein, a neutrophil-derived mediator of vascular leakage, as a prognostic biomarker for risk of progression to severe sepsis with circulatory failure in a multicenter setting.

Design: A prospective international multicenter cohort study.

Setting: Seven different emergency departments in Sweden, Canada, and the United States.

Patients: Adult patients with a suspected infection and at least one of three clinical systemic inflammatory response syndrome criteria (excluding leukocyte count).

Intervention: None.

Measurements and Main Results: Plasma levels of heparin-binding protein, procalcitonin, C-reactive protein, lactate, and leukocyte count were determined at admission and 12-24 hours after admission in 759 emergency department patients with suspected infection. Patients were defined depending on the presence of infection and organ dysfunction. Plasma samples from 104 emergency department patients with suspected sepsis collected at an independent center were used to validate the results. Of the 674 patients diagnosed with an infection, 487 did not have organ dysfunction at enrollment. Of these 487 patients, 141 (29%) developed organ dysfunction within the 72-hour study period; 78.0% of the latter patients had an elevated plasma heparin-binding protein level (> 30 ng/mL) prior to development of organ dysfunction (median, 10.5 hr). Compared with other biomarkers, heparin-binding protein was the best predictor of progression to organ dysfunction (area under the receiver operating characteristic curve = 0.80). The performance of heparin-binding protein was confirmed in the validation cohort.

Conclusion: In patients presenting at the emergency department, heparin-binding protein is an early indicator of infection-related organ dysfunction and a strong predictor of disease progression to severe sepsis within 72 hours.

Heparin-binding protein: a diagnostic biomarker of urinary tract infection in adults

Kjölvmark et al., Open Forum Infect Dis. 2014 Apr 23;1(1).

BACKGROUND: Urinary tract infections (UTIs) are associated with significant morbidity and high frequency of antibiotic prescription. Diagnosing UTI is often difficult, particularly in the critically ill patient and in patients with unspecific and mild symptoms. The standard rapid tests have limited value, and there is a need for more reliable diagnostic tools. Heparin-binding protein (HBP) is released from neutrophils and has previously been studied as a diagnostic and predictive biomarker in different bacterial infections.

METHODS: This prospective survey enrolled adult patients at 2 primary care units and 2 hospital emergency departments, to investigate in urine HBP as a biomarker of UTI. In addition, urine levels of interleukin-6, white blood cells, and nitrite were analyzed and compared with HBP. Based on symptoms of UTI and microbiological findings, patients were classified into different groups, UTI (cystitis and pyelonephritis) and no UTI.

RESULTS: Three hundred ninety patients were evaluated. The prevalence of UTI in the study group was 45.4%. The sensitivity and specificity for HBP in urine as a marker for UTI were 89.2% and 89.8%, respectively. The positive and negative predictive values were 90.2% and 88.8%, respectively. Heparin-binding protein was the best diagnostic marker for UTI, with an area-under-curve value of 0.94 (95% confidence interval, 0.93-0.96). Heparin-binding protein was significantly better in distinguishing cystitis from pyelonephritis, compared with the other markers.

CONCLUSIONS: An elevated level of HBP in the urine is associated with UTI and may be a useful diagnostic marker in adult patients with a suspected UTI.

Elevated plasma levels of heparin-binding protein in intensive care unit patients with severe sepsis and septic shock

Linder et al., Crit Care. 2012 May 21;16(3):R90.

INTRODUCTION: Rapid detection of, and optimized treatment for, severe sepsis and septic shock is crucial for successful outcome. Heparin-binding protein (HBP), a potent inducer of increased vascular permeability, is a potentially useful biomarker for predicting outcome in patients with severe infections. Our aim was to study the systemic release and dynamics of HBP in the plasma of patients with severe sepsis and septic shock in the ICU.

METHODS: A prospective study was conducted of two patient cohorts treated in the ICU at Karolinska University Hospital Huddinge in Sweden. A total of 179 patients was included, of whom 151 had sepsis (126 with septic shock and 25 patients with severe sepsis) and 28 a non-septic critical condition. Blood samples were collected at five time points during six days after admission.

RESULTS: HBP levels were significantly higher in the sepsis group as compared to the control group. At admission to the ICU, a plasma HBP concentration of ≥ 15 ng/mL and/or a HBP (ng/mL)/white blood cell count (109/L) ratio of >2 was found in 87.2% and 50.0% of critically ill patients with sepsis and non-septic illness, respectively. A lactate level of >2.5 mmol/L was detected in 64.9% and 56.0% of the same patient groups. Both in the sepsis group (n = 151) and in the whole group (n = 179), plasma HBP concentrations at admission and in the last measured sample within the 144 hour study period were significantly higher among 28-day non-survivors as compared to survivors and in the sepsis group, an elevated HBP-level at baseline was associated with an increased case-fatality rate at 28 days.

CONCLUSIONS: Plasma HBP levels were significantly higher in patients with severe sepsis or septic shock compared to patients with a non-septic illness in the ICU. HBP was associated with severity of disease and an elevated HBP at admission was associated with an increased risk of death. HBP that rises over time may identify patients with a deteriorating prognosis. Thus, repeated HBP measurement in the ICU may help monitor treatment and predict outcome in patients with severe infections.

Elevated urine levels of heparin-binding protein in children with urinary tract infection

Kjölvmark et al., Pediatr Nephrol. 2012 Aug;27(8):1301-8.

BACKGROUND: Urinary tract infection (UTI) is a common infection diagnosis in children, and efficient diagnosis and treatment are important to avoid serious complications. In this study we investigated whether urinary levels of neutrophil-derived heparin-binding protein (HBP) can be used as a marker of UTI in children. These results were compared to those of dipstick analysis, interleukin-6 (IL-6) analysis in urine, and bacterial culturing.

METHODS: Seventy-eight children aged 0-18 years with fever and/or symptoms indicating UTI were enrolled in a prospective consecutive study. Urine samples were cultured and analyzed with dipstick, and concentrations of HBP and IL-6 were measured.

RESULTS: Fifteen patients were classified as having UTI, 30 patients had fever but were diagnosed with a non-urinary tract infection, and 33 patients had neither UTI nor fever. Using a urine HBP (U-HBP) cut-off level of 32 ng/mL, the sensitivity and specificity for detecting UTI were 93.3 and 90.3 %, respectively. Receiver operating characteristic curves demonstrated that U-HBP levels were a higher specificity indicator of UTI than urine white blood cell counts or urine IL-6 levels; they also showed a higher sensitivity than the results of the urine nitrite test. All patients with significant growth of clinically relevant bacteria had elevated U-HBP levels.

CONCLUSION: The results indicate that rapid analysis of U-HBP can provide helpful guidance in the management of children with suspected UTI.

Increased plasma levels of heparin-binding protein in patients with shock: a prospective, cohort study

Chew et al., Inflamm Res. 2012 Apr;61(4):375-9.

OBJECTIVE: Heparin-binding protein (HBP) is a potent inducer of increased vascular permeability. The purpose of this study was to examine plasma levels of HBP in patients with shock.

DESIGN: Fifty-three consecutive patients with septic and non-septic shock at a mixed-bed intensive care unit were included, as well as 20 age-matched controls. Patients with local infections but without signs of shock served as infectious controls. Enzyme-linked immunosorbent assay was used to determine plasma levels of HBP.

RESULTS: There were no differences in serum HBP levels between healthy controls and those with local infections, including urinary tract infections, pneumonia and gastroenteritis, without shock. Levels of HBP were higher in patients with non-septic shock and septic shock than healthy controls. However, there was no difference in serum HBP levels between patients with septic shock and those with non-septic shock. Moreover, HBP levels were not different between patients with low and high APACHE II scores. Plasma levels of HBP were similar in surviving and non-surviving patients with shock.

CONCLUSIONS: HBP is elevated in patients with shock from septic and non-septic etiologies. Future investigations are required to define the functional role of HBP in patients with shock.

Heparin-binding protein: a diagnostic marker of acute bacterial meningitis

Linder et al., Crit Care Med. 2011 Apr;39(4):812-7. doi: 10.1097/CCM.0b013e318206c396

BACKGROUND: The early detection of bacterial meningitis is crucial for successful outcome. Heparin-binding protein, a potent inducer of increased vascular permeability, is released from activated neutrophils in severe sepsis.

OBJECTIVE: In this study we investigated whether heparin-binding protein levels in cerebrospinal fluid could be used as a diagnostic marker for acute bacterial meningitis.

DESIGN: One prospective and one retrospective patient cohort from two university hospitals in Sweden were analyzed.

SETTING AND PATIENTS: Cerebrospinal fluid samples were collected from 174 patients with suspected central nervous system infection. Thirty-seven patients with acute community-acquired bacterial meningitis, four patients with neurosurgical bacterial meningitis, 29 patients with viral meningitis or encephalitis, seven patients with neuroborreliosis, and 97 control patients were included.


MEASUREMENTS AND MAIN RESULTS: Cerebrospinal fluid samples were analyzed for the concentrations of heparin-binding protein, lactate, protein, glucose, neutrophils, and mononuclear cells. Heparin-binding protein levels were significantly higher (p < .01) in patients with acute bacterial meningitis (median 376 ng/mL, range 12-858 ng/mL) than in patients with viral central nervous system infection (median 4.7 ng/mL, range 3.0-41 ng/mL) or neuroborreliosis (median 3.6 ng/mL, range 3.2-10 ng/mL) or in control patients with a normal cerebrospinal fluid cell count (median 3.5 ng/mL, range 2.4-8.7 ng/mL). In the prospectively studied group, a heparin-binding protein concentration exceeding 20 ng/mL gave a sensitivity of 100%, a specificity of 99.2%, and positive and negative predictive values of 96.2% and 100%, respectively, in diagnosing acute bacterial meningitis. The area under the receiver-operating characteristic curve for heparin-binding protein was 0.994, which was higher than for the other investigated parameters.

CONCLUSION: Elevated cerebrospinal fluid levels of heparin-binding protein distinguish between patients with acute bacterial meningitis and patients with other central nervous system infections.

Roles of heparin-binding protein in bacterial infections

Linder et al., J Innate Immun. 2010;2(5):431-8.

Infectious diseases remain a major health problem, where sepsis and other severe infectious diseases are common causes of morbidity and mortality. The importance of early and appropriate treatment of sepsis and severe bacterial infections has been underlined by the successes of measures like the Surviving Sepsis Campaign, among others. Thus, there is a need for clinical and laboratory tools to identify a patient with severe infection early and to distinguish between bacterial and non-bacterial conditions. Heparin-binding protein (HBP) is also called azurocidin, or cationic antimicrobial protein of 37 kDa (CAP37). It is a multifunctional granule-associated protein that is rapidly mobilized from migrating polymorphonuclear leukocytes. HBP acts as a chemoattractant, an activator of monocytes and macrophages, and induces vascular leakage and edema formation. The release of HBP is triggered by ligation of neutrophilic beta(2)-integrins, a process that may be initiated by bacterial structures. The overall outcome is powerful vascular leakage. It has been shown that patients with severe sepsis express high levels of HBP in plasma before they develop hypotension. HBP is also involved in the pathophysiology of soft tissue infection. In conclusion, this protein is strongly involved in the pathophysiology of severe bacterial infections, and thus represents a potential diagnostic marker and a target for treatment.

Heparin-binding protein: an early marker of circulatory failure in sepsis

Linder et al., Clin Infect Dis. 2009 Oct 1;49(7):1044-50.

BACKGROUND: The early detection of circulatory failure in patients with sepsis is important for successful treatment. Heparin-binding protein (HBP), released from activated neutrophils, is a potent inducer of vascular leakage. In this study, we investigated whether plasma levels of HBP could be used as an early diagnostic marker for severe sepsis with hypotension.

METHODS: A prospective study of 233 febrile adult patients with a suspected infection was conducted. Patients were classified into 5 groups on the basis of systemic inflammatory response syndrome criteria, organ failure, and the final diagnosis. Blood samples obtained at enrollment were analyzed for the concentrations of HBP, procalcitonin, interleukin-6, lactate, C-reactive protein, and the number of white blood cells.

RESULTS: Twenty-six patients were diagnosed with severe sepsis and septic shock, 44 patients had severe sepsis without septic shock, 100 patients had sepsis, 43 patients had an infection without sepsis, and 20 patients had an inflammatory response caused by a noninfectious disease. A plasma HBP level > or = 15 ng/mL was a better indicator of severe sepsis (with or without septic shock) than any other laboratory parameter investigated (sensitivity, 87.1%; specificity, 95.1%; positive predictive value, 88.4%; negative predictive value, 94.5%). Thirty-two of the 70 patients with severe sepsis were sampled for up to 12 h before signs of circulatory failure appeared, and in 29 of these patients, HBP plasma concentrations were already elevated.

CONCLUSION: In febrile patients, high plasma levels of HBP help to identify patients with an imminent risk of developing sepsis with circulatory failure.

Secretion of heparin-binding protein from human neutrophils is determined by its localization in azurophilic granules and secretory vesicles

Tapper et al., Blood. 2002 Mar 1;99(5):1785-93

Human neutrophils have an important role in host defense against microbial infection. At different stages of an infectious process, neutrophils progressively up-regulate receptors and release various effector molecules. These are stored in several distinct types of granules with varying propensity to be secreted. Heparin-binding protein (HBP), also known as CAP37 or azurocidin, is a multifunctional, inactive serine-protease homologue. The present work shows that HBP is released from neutrophils on stimulation with secretagogues that do not trigger the secretion of azurophilic granule content. Therefore, the subcellular localization of HBP was investigated in more detail. Immunofluorescence microscopy revealed that HBP was localized close to the plasma membrane. Further analysis by fractionation of postnuclear supernatants from cavitated neutrophils showed that HBP is stored in azurophilic granules and secretory vesicles but that it is also detected to a minor extent in the plasma membrane. These findings were confirmed by immunoelectron microscopy showing that HBP colocalized with marker proteins of azurophilic granules and secretory vesicles. The presence of HBP in secretory vesicles possibly depends on the stage of cell differentiation, since the promyelocytic cell line HL-60 contains less HBP than mature neutrophils, stored exclusively in the less easily mobilized azurophilic granules. Our findings suggest that HBP can be synthesized or targeted to easily mobilized compartments at a late stage of neutrophil maturation. The ability of neutrophils to secrete HBP from secretory vesicles may be important for proinflammatory functions of this protein, such as the alteration of vascular permeability.